The present invention relates in general to a high-voltage (HT) connector, particularly for providing power to X-ray tubes.
The HT current source for powering an X-ray tube is conventionally encased in a box filled with an insulating and cooling medium, generally a mineral oil, while the X-ray tube is itself also encased in another box filled with an insulating and cooling medium, for example a mineral oil.
Depending on the type of HT current source and the type of X-ray tube, whether it is monopole or symmetric, one or more HT cables convey HT current from the source to the X-ray tube. These power leads are connected to the HT source and to the X-ray tube by means of hermetically sealed HT connectors.
These HT connectors generally consist of two parts, a female part or receptacle which is attached permanently to the box and a male part or plug intended to plug into the receptacle to produce electrical continuity and which constitutes the end of the HT cable.
To withstand the high voltages of the source and of the X-ray tube, which may be as much as 150 kV or more, the receptacle and the plug of the HT connector are made of an insulating material and have shapes and sizes which are generally dictated by international standards.
To protect the users, the boxes of the HT source and of the X-ray tube are earthed and an external jacket of the HT cable is also earthed by metal parts of the receptacle and of the plug.
The HT source and the X-ray tube are electrically connected to the HT cable by interacting metal contacts arranged in receptacle of the connectors.
To avoid electrical discharge between the contacts and the metal parts of the connector of the HT source or of the X-ray tube, the gap between the receptacle and the plug is filled with an electrically insulating fluid, for example a mineral oil or grease such as a silicon oil or grease.
To keep this insulating fluid in the gap between the receptacle and the plug, an annular seal is arranged between the open end of the receptacle and a flange of the plug. As the volume of insulating fluid varies with temperature, and in fact increases as the temperature rises, it is necessary, in order to avoid excessively high pressures which could lead to leaks of insulating fluid and even to the destruction of the receptacle with a risk of HT electrical discharge, that this increase in volume of the insulating fluid be compensated.
To compensate for such variations in volume of the insulating fluid, use is made of a boot/ring, the volume of which varies as a function of the pressure of the insulating fluid in order to accommodate the increase in volume of the insulating fluid.
Furthermore, this annular seal needs to operate over a wide temperature range and be chemically able to resist the hot insulating fluid.
A first boot/ring conventionally used is depicted in FIG. 2. This ring 41 is a ring made of metal which has a accordion side wall 42. This ring is easy to handle and reliable in the long term but is very expensive to manufacture.
Another boot/ring also used is depicted in FIG. 3. This composite ring 43 is composed of a flat metal annulus 44 to which an elastomer annulus 45 is attached, forming a half torus inside the metal annulus 44. This boot/ring is difficult to handle, and requires extremely accurate fitting means to avoid leaks and is expensive.